Means for varying the air-fuel ratio in a fuel injection system for internal combustion engines

ABSTRACT

In a fuel injection system the air-fuel ratio is controlled by a sensor which is disposed in the suction tube of the engine and which is responsive to the quantity of intake air flowing therethrough and controlled by an arbitrarily operable butterfly valve. The air-fuel ratio is alterable as a function of an engine variable by causing the latter to change the flow passage section of a bypass taking out one part of the intake air from the suction tube upstream of the sensor and reintroducing it into the suction tube downstream of the sensor.

United States Patent 1191 Stumpp et a1.

[ 1 Dec. 11, 1973 Inventors:

Assignee:

Filed:

Appl. No.:

Gerhard Stumpp, Stuttgart-Vaihingen; Gregor Schuster, Stuttgart, both of Germany Robert Bosch GmbH, Stuttgart, Germany Apr. 23, 1971 Foreign Application Priority Data Apr. 24, 1970 Germany P 20 19 886.1

[1.8. Cl.l23/ll9 R, 123/139 AW, 123/140 MC,

References Cited UNITED STATES PATENTS 8/1938 Dawes 261/50 A 8/1969 ONeill 2111/44 R 10/1971 Stumpp 261/50 A 12/1971 Knapp 261/50 A Primary Examiner-Wendell E. Burns Attorney Edwin E. Greigg ABSTRACT In a fuel injection system the air-fuel ratio is controlled by a sensor which is disposed in the suction tube of the engine and which is responsive to the quantity of intake air flowing therethrough and controlled by an arbitrarily operable butterfly valve. The air-fuel ratio is alterable as a function of an engine variable by causing the latter to change the flow passage section of a bypass taking out one part of the in- Ilt. Cl. F02!!! 69/00 takeyair from the suction tube upstream of the Sensor held of Search 261/50 50 R; and reintroducing it into the suction tube downstream 123/119 R, 119 0,124 R, 124 A, 124 B, 97

B, 140 MC 14 Claims, 6 Drawing Figures 7 I 1 I I i o l K 27 1 v x rrrrr 6 219 29 l K d H F in I l PAIENIEUDEC a 1 1973 sum 10$ 3 MEANS FOR VARYING THE'AllR-FUEL RATIO IN A FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This'inventi'on relates to a control means for a fuel injection system associated with spark-ignited internal combustion engines. The injection system is of the type wherein fuel isinjected into the suction tube in which there are serially disposed a sensor and an arbitrarily operable butterfly valve. The sensor is moved, in proportion to the flow rate of air, by the difference of the air pressure prevailing upstream and downstream of the sensor. The sensor is deflected by the differential pressure against a constant returning force and, as a function of its deflection, operates a fuel metering valve. In this manner, between the quantity of air and metered fuel there is maintained a certain proportionality which is variable by changing said pressure difference by directing pa'rt'of the intake air through a bypass which circumvents the sensor and which is provided with means for altering its flow passage section.

The purpose of a fuel injection system of the outlined type is'to automatically provide in Otto-engines under 1 all operational conditions anair-fuel mixture which ensures an as perfect a combustion of the fuel as possible.

lnthis manner the highest engine efficiency and lowest possible fuel consumption is ensured and further, the

ternal combustion engine during each operational condition. For this purpose it is necessary to maintain the air-fuel ratio substantially at a constant value and also, to change the same for matching it with the momentary operational condition of the internal combustion engine as a function of operational engine variables such as load, rpm and temperature (the so-called It -correction).

In a known fuel. injection system of the aforenoted type (such as disclosed in German Published Patent Application DOS 1,401,224 the constant air-fuel ratio is obtained by means of a pneumatic servomotor which deflects the sensor as a function of the pressures prevailing upstream and downstream of the sensor. These pressures are a measure of the flow rate in the suction tube. In this known fuel injection system an alteration of the airfuel ratio is obtained by causing the setting magnitudes to exert a torque directly on the pivotal axis of the sensor as a function of the operational engine variables. The torque is codirectional with that of the return force affecting the sensor. Further, the air-fuel ratio may be changed during idling by circumventing the sensor by a bypass, the flow passage section of which may be preset by means of a manually adjustable screw. As soon as the sensor opens in response to an rpm which is higher than the idling rpm, both connections of the bypass channel with the suction tube will be situated downstream of the sensor so that the air-fuel ratio is no longer affected. Thus, in thisknown fuel injection system, to the return force exerted on the sensor which ensures a constant air-fuel ratio (in .this case with the aid of the servomotor), there is superposed a further setting force which varies as a function of the engine variables It -adjustment). It is a disadvantage of such a superposition of the return forces that from a technological point of view it is difficult to obtain the exact desired value of the'sensor adjustment. Furthermore, a control of the aforenoted type isr'elatively complicated and expensive. I

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved control means for a fuel injection system of the aforenoted type wherein the air-fuel ratio is varied in a simple manner as a function of at least one engine variable.

Briefly stated, according to the invention the means controlling the flow passage section of the bypassmay be actuated as a function of theengine variables. lnthis manner the displacement of the sensor occurs sole'ly'as a function of the pressure difference upstream and FIG; 1 is a schematic sectional view of afuelinjection system taken axially along the'suction'tub'e and incorporating a first embodiment of the invention;

FIG. 2 is a sectional view along Il-ll of FIG. 1;

FIG. 3 is a sectional view taken'axially along the suction tube and illustrating a second embodiment of the invention;

FIG. 4 is a sectional view along line lV-lV of FIG. 3;

FIG. Sis a sectional view taken axially along the suction tube and illustrating a third embodime ntof the invention; and FIG. 6 is a sectional FIG. 5.

DESCRIPTION OF THE EMBODIMENTS Turning first to H611, in the fuel injection system shown therein, the intake air flows through an air'filte'r 2 disposed in a housing 1, a suction tubeportion 3 associated with a sensor 4 which moves in a cone-shaped range 5 of the tube portion 3 and through a suction tube portion 6 in which there is disposed an arbitrarily operable butterfly valve 7. The sensor '4 moves'in the conical range 5 of the suction tube portion 3 as an apview taken along line VI-Vl of proximately linear function of the air quantity flowing through the suction tube. The sensor 4 is formed as a plate disposed transversely to the flow direction of "the air. The sensor plate 4 is affixed to a lever'9 to which the displacements of sensor plate 4 are transmitted.

The lever 9 is held withlow friction on a pin 10 and actuates, as a result of its swinging motion, with a lug 13 a movable valve piston 14 which forms part of a fuel metering and distributing valve 15. For opposing the deflection of the sensor 4, fuel under pressure is admitted from a conduit 21 through a branch conduit 21a to the fuel metering valve where it exerts an outwardly directed force to the piston 14. In this manner, the returning force associated with the sensor 4 remains substantially the same regardless of the extent of deflection. The position of rest of the lever 9 is determining by a setting screw 16.

The metering valve 15 is supplied with fuel by a transfer pump 18 which is driven by an electromotor 19 and which draws fuel from a fuel tank 20 through the conduit 21 and advances it to the fuel metering valve 15. A return conduit 22 in which there is disposed a pressure limiting valve 23, extends from the conduit 21 to the fuel tank 20. From the fuel metering valve 15 the metered fuel is admitted through conduits 24 to the individual fuel injection valves which are usually arranged in the suction tube in the vicinity of the associated engine cylinder.

The filter housing 1 and the suction tube portion 3 form an integral structure, so that the air drawn by the engine, after passing through the filter 2, directly impinges upon the surface of the plate 4 which, when the engine is at standstill, closes the inlet of the suction tube. The surface of the sensor plate 4 is expediently substantially larger than the butterfly valve 7 and accordingly, its work capacity is relatively large. In this manner, the sensor 4 is responsive even to small differences of pressure upstream and downstream thereof. Since, in any event, the filter 2 and thus its housing 1 requires a relatively large diameter, the large dimensions of the plate 4 do not necessitate the provision of additional space. The butterfly valve 7, on the other hand, may have relatively small dimensions to take up as little space as possible.

For causing part of the intake air to circumvent the sensor 4, there is provided a bypass 26 which communicates with the suction tube through an opening 27 disposed upstream of the butterfly valve 7. The intake air which in its entirety flows through the butterfly valve 7, may pass in part through the bypass 26 and in part through the sensor 4. The greater the proportion of intake air flowing through the bypass 26, the smaller the deflection of the sensor 4 and the smaller the extent to which the fuel quantity is changed since the fuel quan-' tity is directly proportional to the air quantity passing through the sensor. Thus, by controlling the flow passage section of the bypass 26, the fuel part of the airfuel ratio may be varied. This variation, according to the invention, is effected as a function of at least one engine variable.

According to the embodiment shown in FIGS. 1 and 2, the control of the flow passage section of bypass 26 depends upon the position of the butterfly valve 7. For this purpose there is provided a plate-like, valve member 28 which is keyed normal to the shaft of the butterfly valve 7 and is movable therewith in unison. By virtue of a contour edge 29, the valve member 28 covers the opening 27 between the bypass channel 26 and the suction tube to a greater or lesser extent, dependent upon the angular position of the butterfly valve 7. As seen in FIG. 2, the more the butterfly valve 7 opens, the greater will be the overlap between the valve member 28 and the opening 27 and thus the smaller will be the proportion of the intake air flowing through the bypass 26. In general, under full load conditions the air-fuel mixture should be rich, whereas during idling it should be lean. Such a result, as seen in FIG. 2, is obtained by closing the opening 27 during full load, i.e. when the butterfly valve 7 is fully open. Stated differently, under full load conditions no intake air may flow through the bypass 26 and thus the sensor 4 is deflected to a great extent for a rich fuel-air mixture. Conversely, during idling, when the butterfly valve is almost entirely closed, the bypass 26 is wide open. In FIGS. 1 and 2, the butterfly valve is shown in an approximately middle position which corresponds to an operation under average load conditions.

In FIGS. 3 and 4 there is shown a second embodiment in which too, the control of the flow passage section of the bypass is effected as a function of the position of the butterfly valve. In this embodiment the butterfly valve shaft carries a valve member 28 which has a considerably greater thickness than that of valve member 28 of the first embodiment and which is provided with a contour edge face 31. The valve member 28 is disposed in a chamber 33, one wall of which contains a terminal opening 32 of the bypass 26 and another wall of which contains the opening 27. The valve member 28 is so arranged that, by virtue of its angular position, it controls, with the edge face 31, the flow passage section of the opening 32. The bypass 26 also communicates with chamber 33 by means of a channel 34, the flow passage section of which is variable by means of a setting screw 35. The purpose of this arrangement is to determine, by means of setting screw 35, an intake air quantity which is favorable for idling conditions and which flows continuously through bypass 26. The outline of the opening 32 may be rectangular in which case a particularly advantageous control may be achieved.

A third embodiment of the invention is depicted in FIGS. 5 and 6. Here the control of the flow passage section of bypass 26 is effected as a function of load and temperature conditions. For this purpose there is provided a rotary valve member 37 which is turned as a unit with the butterfly valve 7 with the aid of a driving pin 38 which permits an axial displacement of the valve member 37. The driving pin 38 supports one terminus of a spring 39. The rotary valve member 37 is linearly displaceable against the force of spring 39 by means of a temperature responsive control member 40 which exerts an axially directed force on the shaft of the butterfly valve 7. For the control of the flow passage section of the bypass 26 there are provided an opening 41 in the radial face of the rotary valve member 37 and an opening 42 through which the bypass 26 communicates with a chamber 43 which contains the rotary valve member 37. The chamber 43 communicates with the suction tube through the opening 27.

The outlines of the openings 41 and 42 have a wedgelike configuration so that dependent upon the angular or axial position of the valve member 37, the magnitude of the overlap between openings 41 and 42 varies. For example, as the temperature increases, the rotary valve member 37 is displaced in the direction of the butterfly valve 7 against the force of the spring 39 whereby the area overlap between the openings 41 and 42 is enlarged. Consequently, more air may pass through the bypass 26 whereby a leaner air-fuel mixture is obtained. The temperature responsive control member 40 projects into a space 44 which may form part, for example, of the coolant conduit system of the engine.

The axial displacement of the control member 37 may be effected in lieu of the temperature responsive control member 40 or in addition thereto as a function of the pressure prevailing in the suction tube downstream of the butterfly 'valve 7 or it maybe axially displaced by rpm-responsive hydraulic means. In this manner the displacement of the valve member 37 is also a function of the engine rpm.

For an rpm-responsive control of the flow passage section of the bypass 26 of the embodiment shown in FIGS. 5 and 6, there is provided a chamber 47 which communicates with the chamber 43 through an opening 46 and with the suction tube through an opening 48. The'latter is situated downstream of the butterfly valve 7. The opening 46 is controlled-by the lateral face' pressure prevailing in the space 43. For this purpose there is provided a bore 51.

"When the vehicle is coasting in gear, the butterfly valve 7 is closed and consequently, because of the significant vacuum prevailing downstream of the butterfly valve 7, the piston 49 is shifted into a position in which it'closes the opening 46, so that the sensor 4 will not be deflected at all. During idling, on the other hand,.in an appropriate dimensioning of the cross, section of the piston 49 and the strength of the spring50, the connection 46, 47, 48 may serve as an idling channel: the intake air may flow through the opening 27, the space 43 and the connection 46, 47, 48 without being controlled by the butterfly valve 7 while the sensor 4 undergoes a deflection which corresponds to the idling operation. As soon as there is generated a lower pressure in the suction tube downstream of the butterfly valve 7 because of the increased rpm, the connection 46, 47, 48 is'closed in this particular instance. By means ofa set ting screw 52 the initial position of the piston 49 may be varied in such a manner that the thus determined remaining flow passage section of the opening 46 affects th'e'fuel-air ratio in a desired manner. It is to be understood that in lieu of a piston 49 an equivalent membrane control may be provided in association with the connection 46, 47, 48.

What is claimed is:

1. In a fuel injection system associated with a sparkignited internal combustion engine and being of the known type that includes (a) an'arbitrarily operable butterfly valve disposed in the suction tube of said engine to vary the quantities of intake air drawn by said engine through said suction tube, (b) a fuel metering pump, a sensor disposed in said suction tube at a distance from said butterfly valve, said sensor is deflected against a return force in proportion to said quantities of intake air by the difference of the pressures upstream and downstream of said sensor, (d) means for connnecting said sensor to said fuel injection pump to control the metering of fuel as a function of the deflection of said sensor and to determine an airfuel ratio, (e) a bypass circumventing said sensor and adapted to take out intake air from said suction tube upstream of said sensor and to reintroduce the same into said suction tube downstream of said sensor and (f) means for controlling the flow passage section of 6 said bypass to change the quantities of intake air passing through said sensor and thus vary the air-fuel ratio, the improvement in the last-namedmeans comprising,

A. a movable valve member disposed in said bypass to vary the flow passage section thereof,and

B. means for automatically moving said valve member as a function of the position of said butterfly valve.

2. An improvement as defined inclaim 1, including means for moving said valve member as a function of the pressure prevailing in said suction tube downstream of said butterfly valve.

3. An improvement as defined in claim 1, including means for moving said valve member as a function of the engine temperature.

4. An improvement as defined in'claim 1, wherein said valve member is formed of a plate-like component rotatable about an axis normal thereto for varying the flow passage section of said'bypass.

5. 'An improvement as defined in claim 4, including a rotatable shaft carrying said butterfly valve; said valve member is affixed to said shaft to be moved in-unison with said butter-fly valve.

6. An improvement as defined in claim 4, including A. an opening forming part of said bypass,

B. aplanar face forming part of said plate-like component and extending normal to said axis and C. a contour edge forming part of said plate-like component and cooperating with said opening whereby said planar face covers said-opening to'an extent dependent upon the angular positionof said plate-like component.

7. An improvement as defined in claim 4,-including A. an opening forming part of said bypass and B. a contour edge face forming part of said valve member and extending parallel to said axis; said contour edge face determines said flow passage section'of said bypass at said opening in cooperation therewith.

8. An improvement as defined in claim 1, including A. a first wedge-shaped opening providedin said movable valve member,

B. a second, stationary wedge-shaped opening forming part of said bypass and overlapping said first opening to constitute therewith a variable flow passage section of said bypass,

C. means for rotating said valve member about an axis and associated with a first engine variable, and

D means for displacing said valve member along said axis and associated with a second engine variable; said flow passage section is varied by virtue of the rotary and linear motion of said valve member.

9. An improvement as defined in claim 7, wherein said means defined in (D) is a temperature-responsive component.

10. An improvement as defined in claim 1, wherein said butterfly valve is disposed downstream of said sensor.

11. An improvement as defined in claim 1, including connecting means for establishing communication between said bypass and said suction tube downstream of said butterfly valve, said improvement includes a control means for varying the flow passage section of said connecting means in response to the pressure in said suction tube downstream of said butterfly valve.

12. An improvement as defined in claim 11, wherein said control means is formed as a piston displaceable in response to the pressure in said suction tube downstream of said butterfly valve.

13. An improvement as defined in claim 8, including connecting means for establishing communication between said bypass and said suction tube downstream of said butterfly valve, said connecting means extends towards the suction tube from a location in said bypass which is downstream from said first and second openings, said improvement includes a control means for varying the flow passage section of said connnecting 

1. In a fuel injection system associated with a spark-ignited internal combustion engine and being of the known type that includes (a) an arbitrarily operable butterfly valve disposed in the suction tube of said engine to vary the quantities of intake air drawn by said engine through said suction tube, (b) a fuel metering pump, (c) a sensor disposed in said suction tube at a distance from said butterfly valve, said sensor is deflected against a return force in proportion to said quantities of intake air by the difference of the pressures upstream and downstream of said sensor, (d) means for connnecting said sensor to said fuel injection pump to control the metering of fuel as a function of the deflection of said sensor and to determine an air-fuel ratio, (e) a bypass circumventing said sensor and adapted to take out intake air from said suction tube upstream of said sensor and to reintroduce the same into said suction tube downstream of said sensor and (f) means for controlling the flow passage section of said bypass to change the quantities of intake air passing through said sensor and thus vary the air-fuel ratio, the improvement in the last-named means comprising, A. a movable valve member disposed in said bypass to vary the flow passage section thereof, and B. means for automatically moving said valve member as a function of the position of said butterfly valve.
 2. An improvement as defined in claim 1, including means for moving said valve member as a function of the pressure prevailing in said suction tube downstream of said butterfly valve.
 3. An improvement as defined in claim 1, including means for moving said valve member as a function of the engine temperature.
 4. An improvement as defined in claim 1, wherein said valve member is formed of a plate-like component rotatable about an axis normal thereto for varying the flow passage section of said bypass.
 5. An improvement as defined in claim 4, including a rotatable shaft carrying said butterfly valve; said valve member is affixed to said shaft to be moved in unison with said butterfly valve.
 6. An improvement as defined in claim 4, including A. an opening forming part of said bypass, B. a planar face forming part of said plate-like component and extending normal to said axis and C. a contour edge forming part of said plate-like component and cooperating with said opening whereby said planar face covers said opening to an extent dependent upon the angular position of said plate-like component.
 7. An improvement as defined in claim 4, including A. an opening forming part of said bypass and B. a contour edge face forming part of said valve member and extending parallel to said axis; said contour edge face determines said flow passage section of said bypass at said opening in cooperation therewith.
 8. An improvement as defined in claim 1, including A. a first wedge-shaped opening provided in said movable valve member, B. a second, stationary wedge-shaped opening forming part of said bypass and overlapping said first opening to constitute therewith a variable flow passage section of said bypass, C. means for rotating said valve member about an axis and associated with a first engine variable, and D means for displacing said valve member along said axis and associated with a second engine variable; said flow passage section is varied by virtue of the rotary and linear motion of said valve member.
 9. An improvement as defined in claim 7, wherein said means defined in (D) is a temperature-responsive component.
 10. An improvement as defined in claim 1, wherein said butterfly valve is disposed downstream of said sensor.
 11. An improvement as defined in claim 1, including connecting means for establishing communication between said bypass and said suction tube downstream of said butterfly valve, said improvement includes a control means for varying the flow passage section of said connecting means in response to the pressure in said suction tube downstream of said butterfly valve.
 12. An improvement as defined in claim 11, wherein said control means is formed as a piston displaceable in response to the pressure in said suction tube downstream of said butterfly valve.
 13. An improvement as defined in claim 8, including connecting means for establishing communication between said bypass and said suction tube downstream of said butterfly valve, said connecting means extends towards the suction tube from a location in said bypass which is downstream from said first and second openings, said improvement includes a control means for varying the flow passage section of said connnecting means in response to the pressure in said suction tube downstream of said butterfly valve.
 14. An improvement as defined in claim 1, including A. a channel forming part of said bypass and circumventing said movable valve member and B. means for varying the flow passage section of said channel independently from said movable valve member. 